Remote monitoring of data is frequently used in industrial settings. The desire for implementing such monitoring ranges from the need for centralised monitoring of relatively complex industrial systems to the convenience of allowing a small number of operators to monitor multiple data streams via a single workstation. In many cases, it is also desirable that the HMI allow operators to control at least some of the industrial processes and machines in relation to which the data is being collected.
Historically, collection and display of industrial data on operator workstations has been dealt with on a proprietary basis, with application-specific software linking remote data sources with dedicated terminals. Whilst such systems have provided satisfactory performance, they are relatively time consuming to design, and relatively inflexible once implemented.
Another problem is that individually implemented software solutions are often limited in the types of data sources with which they can interface.
One of the most profound developments of the last five years has been the staggering growth of the internet. This growth has changed public perceptions about the availability of data, about what to expect in a user interface, and how open and interoperable computer systems should be. Standalone computer systems are no longer acceptable to the market—the increasingly networked world is setting the pace and scope of change.
In addition, this growth has led to a huge shift in development focus for practically every software organisation. The web has become the ubiquitous data delivery mechanism, and as software organisations focus their energies on harnessing its potential, the technologies which underpin its success are being pushed forward at ever-increasing rates. Where once the web was not mature enough to support mission-critical functions, such as major financial transactions or process control, it is clear that this is no longer the case.
It is this growth which is driving investment into user interface technology, as the major stakeholders seek to establish the internet as a viable business platform. As a result, current technological trends have meant the underlying technologies are becoming increasingly more appropriate to the field of industrial process control.
The development of what may be loosely termed “internet technologies” has been extremely rapid, and has a very short history:                December 1993: Only 200 known http servers existed.        December 1994: First W3C meeting. Over 200 members, charter to promote interoperability.        October 1996: OLE Controls 96 Specification published. Promotes lightweight, windowless controls suitable for the web environment, and intended to add increasing sophistication to browser capabilities.        December 1996: Cascading Style Sheet specification. Introduced 2D positioning, size, colour, font attributes.        July 1997: HTML 4.0 specification. Included scripts, objects, framesets, internationalisation. Browser technology advanced appropriately.        September 1997: Dynamic HTML, Document Object Model. Full access to the HTML object model, providing web pages with unprecedented power and flexibility.        September 1998: Internet Explorer 5.0 Beta 2. Includes Vector Markup Language for vector graphics capabilities.        late 1999: Office 2000 to use HTML/XML as document format for all suite products. Microsoft look to include sufficient functionality in HTML for it to be suitable for use by Visual Basic forms engine.        
In parallel with these developments has been an increasing awareness that HTML's origins as a language intended to store presentation information means its ability to store and represent data is severely limited. This limitation has led to the rise of XML, or extensible Markup Language, intended to work in concert with HTML to provide a means of storing both data and presentation information.
It was these trends that led the applicant to consider the suitability of such technologies for industrial control systems.
The development requirements of an industrial control system indicate clearly that known web browsers are not suitable for the operator environment of an industrial control system. They may be acceptable for casual use, but the operator environment has specific requirements, such as restricted navigation, support for industrial keyboards, alarm and status indication, and security.
The partial solution to a number of these issues may be provided using a software package sold and marketed by Microsoft®. In particular, Microsoft® supply a rendering engine used in Internet Explorer (known as MSHTML), for use by third-party developers wishing to integrate HTML rendering capabilities into their applications. While this software package can represent a useful tool for system designers, its generic nature ensures that it will not automatically integrate or interact with other applications. Further although the invention in some aspects will be described in relation to this software package, it will be appreciated that other browser techniques may be used.
Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.